Application of Electrical Resistivity Tomography in Subsurface Building Foundation Study

Eshimiakhe D, Sani G and Osumeje J

Published on: 2022-12-27

Abstract

Knowledge of the probable cause of rampant failure of building foundations due to subsurface movements that give rise to cracks and structural differential settlements is now of great concern to geoscientists. Some part of Federal University Gusau, Zamfara state Nigeria, was investigated to explore the suitability of the subsurface for the foundations of buildings and also to identify weak zones that may be prone to subsidence due to lack of competence to support massive structures. This investigation was achieved using 2D electrical resistivity tomography. The data were obtained using a Terrameter SAS 4000 and ES 464 electrode selector equipment and processed using the RES2DINV software. A Wenner configuration at electrode spacing of 5 m was used to acquire the data along five profiles in the study area. Correlating the result with borehole data showed that the subsurface has a minimum of three and a maximum of four geo-electric sections. The overburden layer is composed of laterite and clay with resistivity ranges of 26 ?m- 394 ?m and 24 ?m- 108 ?m respectively. The weathered basement has a resistivity range of 400 ?m- 735 ?m (8-13 m in thickness) and the fresh basement has a resistivity range of 201 ?m – 735 ?m (15 m in thickness). It is concluded that the most competent layer as suggested by the investigation is the fresh basement because of its high resistivity value (746 ?m – 1206 ?m). In the overburden, low resistivity clay formation should be avoided. This is because the clay materials are subject to differential settlement or flow under pressure.